1. Field of the Invention
This invention relates to a method for molding a tape-form nonwoven web into a molded form and an apparatus therefor. It also relates to a method for making a molded cushioning article from the molded form of a tape-form nonwoven web, and an apparatus therefor.
The molded cushioning article is useful as a cushioning material for seats of vehicles, furniture such as chairs, or the like.
2. Description of the Related Art
Methods hitherto known for manufacturing cushioning materials for seats of vehicles, furniture or the like include: that urethane is foamed and shaped into a predetermined form in a mold, thereby providing an urethane foam cushioning; that a fiber web material is applied with a liquid adhesive, and then packed in a mold wherein the adhesive is cured (for example, Japanese Unexamined Patent Publication No.62-102712); that air flow accompanied with staple fibers having incorporated therein heat-bondable fibers are injected into a mold where the staple fibers are thermoformed (for example, Japanese Unexamined Patent Publication No. 3-121091); and that, instead of the conventional wadding, a sliver composed of only crimped staple fibers serving as a matrix is shaped into a spiral or wavy form and filled into a covering material, or the sliver is adhered to a cloth to improve the compression chracteristics or other properties of cushioning articles (Japanese Unexamined Utility Model Publication No.49-9512 and Japanese Unexamined Patent Publication No.50-70165).
However, the manufacturing of urethane foam necessitates troublesome handling of chemicals used, and sometimes needs use of freon thereby causing a problem of an environmental pollution. Also, in order to obtain urethane foam cushioning articles molded in a uniform shape, a liquid mixture of a polyurethane-forming monomer and a foaming agent, when injected into a cavity of a closed mold of a predetermined shape and foamed therein, needs to be well extended over the whole mold cavity while being foamed. Hence, the mold is required to have a precise shape with even strictly defined positions of apertures through which extra urethane is discharged. Also, the liquid mixture generally cannot be injected in a manner such that the liquid is directed separately for each of specific parts of the mold, so that the hardness of the cushioning article varies correspondingly to the stress applied to the seat part of the cushion or the hardness therof varies locally as the seating part being soft and the peripheral part being hard. Therefore, a molded seat cushion cannot be obtained which is superior in load supporting efficiency, comfort and shape-keeping properties. Further, since the urethane foam cushion is structured with a uniform polymeric foam shows such a particular property that it feels lard when initially seated and thereafter the urethane foam becomes indented drastically due to lowered modulus from quick extension of collapse of cells. Hence, the urethane foam cushion has a poor cushioning efficiency and feels easily flattened in use. Also, the urethane foam is likely to be formed with films among the cells, rendering the air-permeability thereof poor and making the cushion easily stuffy. Therefore, the urethane foam is not desirable as a cushioning material. Further, since urethane polymers are soft and foamed, the urethane foam requires a higher density to have resistance against compression, and that urethane is easily affected by humidity and light to be deteriorated of physical properties. In these days, particularly, the urethane foam suffers such a problem of environmental pollution that the urethane foam when discarded after use cannot be burnt due to evolution of black smoke and poisonous gas and is hard to be recycled, so that it is usually buried under the ground.
With the manufacturing method for a cushioning article in which a fiber web is first applied with a liquid adhesive and packed in the mold for curing and molding, the operation is carried out in a wet process, resulting in poor working environment, particularly in use of a solvent. Also, it cannot be avoided that in packing the fiber web previously applied with an adhesive in the mold it is molded in the state of being compressed by adhesion or a similar manner, or the adhesive is applied non-uniformly. Furthermore, fibers of the web are hard to move and hard to be entangled to one another at joints of adjacent webs or between adjacent layers of webs since they are wet. As a result the web layers are adhered to one another weakly. The method has also problems of degradation of product quality due to contamination of the mold, and a higher poduction cost and a poor productivity due to the fact that handling the fiber web is difficult to be mechanized and necessarily requires man-power.
With the method wherein an air flow accompanied with staple fibers having incorporated therein heat-bondable fibers are injected, into a mold where the staple fibers are thermoformed for providing cushion product, the fibers must be uniformly scattered in the air flow injected into the mold. However, when the fiber concentration in the air flow is low, it takes a long time for a predetermined amount of fibers to be injected, leading to a problem of a poor productivity. The fibers when increased in concentration are entangled to one another due to crimp of the fibers to become lumps of fibers which, when injected, cause undersirable nonuniformity in density of fibers in the cushion structure. Reducing the crimping degree of fibers to avoid the above problems leads to a problem that the injected fibers do not have sufficient bulkiness, and increasing the smoothness of fiber surfaces is likely to have a problem of insufficient adhesion in thermoforming process.
Further important problems arise in the above method as follow. The staple fibers are injected in the mold by a feeding fan or the like while being separated by a card or a fiber opener. When the staple fibers are injected into a covering material or mold of a complicated shape, the fibers along with air flow enter the mold or covering material, while flowing with a straight-line motion, so that the wadding Of fibers is hard to be controlled of weight for specific parts of the molded form. Also, the method uses a long passage of feed from the card or opener to the injecting point into the mold and, hence, it takes time to control weight of the stuffing in the feeding course or to stop and start feeding the fibers.
With the method of shaping a sliver into a spiral or wavy form and forming it in a sheet-like configuration, there is provided no adhesion among fibers or slivers to cause a formed product to be easily collapsed, resulting in poor compression durability. Also, the formed product is hard to be partially given special shape or partially controlled of density, thereby merely providing flat-form products. Hence, it does not provide a cushioning material for seats of vehicles or funiture such as being superior in comfort in use based on an improved fitting efficiency to human body and weight-supporting efficiency obtained by partially giving a special shape to the cushioning material or partially varying the hardness thereof. Also, in shaping the sliver into a spiral form, since the sliver itself is superposed on one another and spiraled, it causes gaps among specific parts of the sliver or intersecting parts of the slivers to have a higher density than the rest. The sliver when shaped into a wavy form is likely to have gaps at the folded parts and fibers are arranged much in the direction of being compressed, so that the resulting cushioning material easily buckles and has a low durability. Also, the sliver to be shaped into a wavy form must be combined with a covering material or a plain sheet in molding and, thus, there are great limitations to manufacturing conditions, kinds of molded forms and productivity.